mineral

Mother of Pearl (Nacre)

Aragonite (CaCO3) with Organic Matrix

Hardness: 3.5-4.5 (Mohs scale); Color: Iridescent white, cream, or pale pink; Luster: Pearly/Iridescent; Structure: Orthorhombic (plates); Cleavage: None but brittle; Specific Gravity: 2.72-2.85

Hardness: 3
Color: Iridescent white, cream, or pale pink
Luster: Pearly/Iridescent

Identified March 20, 2026More mineral →

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Physical properties

Hardness: 3.5-4.5 (Mohs scale); Color: Iridescent white, cream, or pale pink; Luster: Pearly/Iridescent; Structure: Orthorhombic (plates); Cleavage: None but brittle; Specific Gravity: 2.72-2.85

Formation & geological history

An organic-inorganic composite material produced by some mollusks (oysters, mussels, abalones) as an inner shell layer. It forms as the mollusk continuously deposits thin, overlapping layers of aragonite separated by organic polymers like conchiolin.

Uses & applications

Predominantly used for buttons, jewelry, watch faces, architectural inlays, and decorative items. In some cases, powdered nacre is used in cosmetics and pharmaceuticals.

Geological facts

Nacre's iridisence is caused by the thickness of the aragonite platelets being close to the wavelength of visible light; historical and luxury clothing often features these buttons, following a long tradition of utilizing seashell byproducts.

Field identification & locations

Identify in the field by its characteristic iridescence (play of colors) and flat, circular shape with man-made holes (in the case of buttons). Found in marine and freshwater environments globally. Collectors look for thickness, color consistency, and lack of chipping.

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